1. Field of the Invention
The invention relates to a switching arrangement in particular for power switches such as those which are used in power plants, transformer substations and other electrical power supply facilities, in order to switch operating and excess currents on and off, and to a method for its production.
2. Discussion of Background
Switching arrangements of the generic type are known, in which in particular parts of switching contacts on which the roots of the arc which is formed during switching are situated consist of material which is particularly resistant to contact erosion. Such material is usually produced by sintering a mixture of metal powders e.g. tungsten as a high-melting component and copper as a lower-melting component. This sintered material is relatively difficult to process. In particular, it is extremely brittle and can only be shaped by means of processors which remove metal. It cannot be welded in a customary manner and can only be joined to other materials by comparatively complicated processes, for example by having copper cast behind it, by friction welding, by flush butt welding or electron beam welding or by soldering which, however, produced a comparatively weak joint, or may be removably joined by means of a screw connection, which, however, requires complicated machining. The provisions of parts or coatings which are resistant to contact erosion therefore generally requires a high level of outlay.
Since in practice the material which is resistant to contact erosion cannot be deformed, the possibilities for shaping a base body which is to be provided with a coating which is resistant to contact erosion are extremely limited. Owing to the brittleness of the material, it is also impossible to provide flexible parts with a coating which is resistant to contact erosion. For these reasons, it is generally deemed sufficient, for example, to use tips of switching pins, arcing rings and similarly simple parts which are made from material which is resistant to contact erosion. Other parts of the arcing chamber and areas which adjoin the latter, which are also exposed to the hot gases generated when opening the switch, on the other hand, remain unprotected.